It is known in the art to combine two or more polymers to form one blend having the desirable properties of its constituents. There has been research in the field to find compatible polymers or, in the alternative, compatibilizers for incompatible polymers. In many cases it can be more advantageous to use compatibilizers to promote miscibility between polymers than to produce completely new polymer compositions. The term compatilization refers to the improvement of any desirable property by blending. Examination of a polymer's phase behavior is used to determine the degree of miscibility of the blends.
In particular there has been much interest in the art in providing compatibilizers for blending various polyesters with bisphenol-A polycarbonate. One polyester which, it is believed, would provide a beneficial blend with polycarbonate is poly(ethylene)terephthalate, however, it appears that work in the art would indicate the immiscibility of these two polymers. See Pilati, F., Marianucci, E., and Berti, C. J. Appl. Polym. Sci., 30, 1267 (1985); Hanrahan, B. D., Angeli, S. R., and Runt, J., Polym. Bulletin (Berlin), 15, 455 (1986); Huang, Z. H. and Wang, L. H. Makromol. Chem., Rapid Commun., 7, 255 (1986); and Henrichs, P. M., Tribone, J., Massa, D. J., and Hewitt, J. M., Macromolecules, 21, 1282 (1988).
Other work indicates very limited miscibility of these two polymers. See Nassar, T. R., Paul, D. R., and Barlow, J. W., J. Appl. Polym. Sci., 23, 85 (1979); Murff, S. R., Barlow, J. W., and Paul, D. R., J. Appl. Polym. Sci., 29, 3231 (1984); and Kim, W. and Burns, C., J. Polym. Sci.: Part B, 28, 1409 (1990).
In "Polymer Blends", (Eds. D. R. Pauland S. Newman), Academic Press, New York, 1978, D. R. Paul reviews compatibilizing agents which can enhance the compatibility of polymer-polymer systems. Incompatibility of polymers can be overcome by introduction of a suitable compatibilizing agent, i.e. block or graft copolymers having segments of similar structure or solubility parameter as the polymers being mixed. Where the different segments are not chemically identical, the desired effect may still result if one of the segments of the block or graft is miscible with one of the phases.
It would be very beneficial in the field of polymer blending to identify agents which could overcome the immiscibility of polymer-polymer systems. In particular, it would be a distinct advance in the art if a composition were available which functioned to promote the compatibility of poly(ethylene)terephthalate and Bisphenol-A polycarbonate and to enhance the crystallization of Bisphenol-A polycarbonate.